Sulfotransferases are enzymes that catalyze the transfer of a sulfate from a donor compound to an acceptor compound, usually placing the sulfate moiety at a specific location on the acceptor compound. There are a variety of different sulfotransferases which vary in activity, i.e. with respect to the donor and/or acceptor compounds with which they work. Known sulfotransferases include those acting on carbohydrate: heparin/heparan sulfate N-sulfotransferase (NST); chondroitin 6/keratan 6 sulfate sulfotransferase (C6ST/KSST); galactosylceramide 3′-sulfotransferase; heparan sulfate 2-sulfotransferase (Iduronic acid); HNK-1 sulfotransferase (3-glucuronic acid); heparan sulfate D-glucosamino 3-O-sulfotransferase (3-OST); etc., as well as those acting on phenols, steroids and xenobiotics: aryl sulfotransferase I & II, hydroxy-steroid sulfotransferases I, II & III, dehydroepiandrosterone (DHEA); etc. Sulfotransferases play a central role in a variety of different biochemical mechanisms, as the presence of a sulfate moiety on a particular ligand is often required for a particular activity, e.g. binding.
The presence of a sulfate moiety on selectin ligands has been shown to be important for selectin binding to occur. See Imai et al., Nature (1993) 361:555-557 and Imai et al., Glycoconjugate J. (1993) 10:34-39, as well as U.S. Pat. No. 5,695,752. Several selectin ligands have, to date, been identified. The L-selectin endothelial ligands in mouse that have been identified are: CD34, GlyCAM-1, MAdCAM-1 and sgp200. In addition, PSGL-1 has been identified as a leukocyte ligand for P-, E-, and L-selectin. Endothelial ligands for L-selectin in humans are still poorly defined, but include CD34 and podocalyxin.
Selectin mediated binding plays an important and prominent role in a variety of biological processes. Selectins are lectin like cell adhesion molecules that mediate leukocyte-endothelial, leukocyte-leukocyte, leukocyte-platelet, platelet-endothelial and platelet-platelet interactions. One critical biological process in which selectin mediated binding plays a role is the maintenance of immune surveillance.
Maintenance of immune surveillance depends on the constant recirculation of lymphocytes from the blood through the vascular wall into the tissues and eventually back into the blood. Lymphocyte recruitment from the blood into all secondary lymphoid organs (except the spleen) as well as into many sites of chronic inflammation is mediated by a specialized postcapillary venule called a high endothelial venule. These vessels are defined by the distinct, cuboidal morphology of their endothelial cells and their luminal presentation of ligands for the leukocyte adhesion molecule, L-selectin. This lectin-like adhesion molecule is expressed on all classes of leukocytes in the blood and is responsible for the initial tethering and rolling of a leukocyte on the endothelium prior to subsequent integrin mediated firm arrest and transmigration.
Although selectin mediated binding events play a critical role in normal physiological processes, disease conditions do exist for which it is desired to regulate or modulate, e.g. limit or prevent, the amount of selectin mediated binding that occurs. Such conditions include: acute or chronic inflammation; autoimmune and related disorders, tissue rejection during transplantation, and the like.
As the above conditions all result from selectin mediated binding events, there is great interest in the elucidation of the mechanisms underlying such binding events. There is also great interest in the identification of treatment methodologies for these and related disease conditions, as well the identification of active agents for use therein.
As such, there is continued interest in the identification of participants in the selectin binding mechanism, including enzymatic agents, and the elucidation of their role(s) in selectin mediated binding events, as well as the development of therapies for disease conditions arising from such binding events.
Relevant Literature
Chondroitin-6-sulfotransferase is disclosed in EP 821 066, as well as in Fukuta et al., “Molecular Cloning and Characterization of Human Keratan Sulfate Gal-6-Sulfotransferase,” J. Biol. Chem. (Dec. 19, 1997) 272: 32321-32328; Habuchi et al., “Enzymatic Sulfation of Galactose Residue of Keratan Sulfate by Chondroitin 6-Sulfotransferase,” Glycobiology (January 1996) 6:51-57; Habuchi et al., “Enzymatic Sulfation of Galactose Residue of Keratan Sulfate by Chondroitin 6-Sulfate by Chondroitin 6-Sulfotransferase,” Glycobiology (January 1996) 6:51-57; Fukuta et al., “Molecular Cloning and Expression of Chick Chondrocyte Chondroitin 6-Sulfotransferase,” J. Biol. Chem. (1995) 270: 18575-18580; and Habuchi et al., “Purification of Chondroitin 6-Sulfotransferase Secreted from Cultured Chick Embryo Chondrocytes,” J. Biol. Chem. (1993) 268: 21968-21974.
References providing background information on selectin mediated binding include: Baumhueter et al., “Binding of L-Selectin to the Vascular Sialomucin CD34,” Science (Oct. 15, 1993): 436-438; Boukerche et al., “A Monoclonal Antibody Directed Against a Granule Membrane Glycoprotein (GMP-140/PADGEM, P-selectin, CD62P) Inhibits Ristocetin-Induced Platelet Aggregation,” Br. J. Haematology (1996) 92: 442-451; Celi et al., “Platelet-Leukocyte-Endothelial Cell Interaction on the Blood Vessel Wall,” Seminars in Hematology (1997) 34: 327-335; Frenette et al., “Platelets Roll on Stimulated Endothelium In Vivo: An Interaction Mediated by Endothelial P-selectin,” Proc. Natl. Acad. Sci. USA (August 1995) 52:7450-7454; Girard & Springer, “High Endothelial Venules (HEVs): Specialized Endothelium for Lymphocyte Migration,” Immun. Today (1995) 16: 449-457; Hemmerich et al., “Sulfation Dependent Recognition of High Endothelial Venules (HEV)-Ligands by L-Selectin and Meca79, and Adhesion-Blocking Monoclonal Antibody,” J. Exp. Medicine (December 1994) 180: 2219-2226; 262 Lasky et al., “An Endothelial Ligand for L-Selectin Is a Novel Mucin-Like Molecule,” Cell (Jun. 12, 1992) 69:927-938; Rosen & Bertozzi, “The Selectins and Their Ligands,” Current Opinion in Cell Biology (1994) 6: 663-673; and Sawada et al., “Specific Expression of a Complex Sialyl Lewis X Antigen On High Endothelial Venules of Human Lymph Nodes: Possible Candidate for L-selectin Ligand,” Biochem. Biophys. Res. Comm. (May 28, 1993) 193: 337-347; as well as U.S. Pat. No. 5,580,862.
U.S. Pat. No. 5,695,752 describes methods of treating inflammation through administration of sulfation inhibitors.